Field glasses are predominantly obtainable with a binocular embodiment so as to be able to observe distant objects in a magnified manner with both eyes. For this purpose, conventional analog field glasses are typically embodied with a lens configuration, for example, as so-called theater or opera glasses, or as prism field glasses. Conventional analog field glasses consist of two telescopes connected to one another, each with an objective, a prism system and an eyepiece. In each one of the two telescopes, an intermediate image generated by the objective is observed by way of the associated eyepiece, wherein the eyepiece generates an image on the retina together with the respective ocular lens of the user.
In digital field glasses—which are sometimes also referred to as electronic field glasses—the objective initially images onto an electronic image sensor, for example, a CCD or CMOS chip with resolving power in two dimensions. The image thus recorded digitally or electronically by the image sensor can be processed digitally or electronically and displayed on one or more electronic displays. Digital field glasses often only have one objective and only one image sensor, the image of which is displayed on a left-hand and right-hand display. Although such field glasses only have one objective, they nevertheless have a left-hand and right-hand eyepiece so that the user can observe the left-hand display through the left-hand eyepiece with the left eye and the right-hand display through the right-hand eyepiece with the right eye. Since such digital field glasses have two eyepieces, these can also be referred to as digital binocular field glasses, even though only one objective is present. By way of example, an advantage of digital field glasses is that the observed image can also be recorded, for example, filmed, and stored electronically at the same time as the binocular observation, without further optical outlay. Moreover, binocular field glasses can contain further optical or electronic components, such as for example, an image stabilizer.
In order to adapt the lateral eyepiece distance in the case of binocular field glasses to the individual distance between the eye pupils of the user, the so-called interpupillary distance, the bridge of the field glasses can be embodied as a so-called folding bridge. In the case of field glasses with a folding bridge, the two eyepieces are connected to one another in a pivotable manner by way of a hinge device of the folding bridge with at least one pivot hinge. Hence, the eyepiece distance is adapted to the individual interpupillary distance by the user via the pivot movement of the two eyepieces. A typical interval for the adjustment of the eyepiece distance can lie in the region of approximately 55 mm to 75 mm.
Relatively large field glasses typically have a hinge device with a single central pivot hinge, on which the two eyepieces are pivoted downward in an equal but opposite manner in order to reduce the eyepiece distance. In the case of smaller field glasses, the folding bridge often has a rigid central bridge part and a first and second decentralized pivot hinge for the first or second eyepiece, wherein the first and second decentralized pivot hinge are pivotable independently of one another such that each one of the two eyepieces can be pivoted independently of the respective other eyepiece. Such field glasses are often referred to as compact field glasses.
Typically, the image sensor and the two displays are rectangular and the image recorded by the image sensor is displayed on the two displays one-to-one in relation to the rectangular form of the image sensor and of the displays. That is, the orientation of the displayed image relative to the display is maintained, independently of the position of the folding bridge and hence independently of the absolute orientation of the display relative to the horizontal. Expressed differently, the image displayed by the display and observed by the user rotates together with the display about an axis parallel to the optical axis relative to the horizontal when the user adjusts the folding angle of the folding bridge. This leads to the left-hand image rotating together with the left-hand display in a counterclockwise direction and the right-hand image rotating together with the right-hand display in a clockwise direction when the user pivots the two eyepieces downward and reduces the pivot angle of the folding bridge in order thus to reduce the eyepiece distance. The rotation of the image observed by the user connected therewith is typically unwanted.
The documents JP 11-064740 and JP 11-112851 each describe binoculars with a digital camera. An image tilt in the context of a folding bridge position is not considered.
JP 2004-191861 describes a binocular system, in which an imaging element is introduced into the beam path in order to record an image. The system contains means for determining the rotational angle in the form of a conductive pattern. Image data are corrected by segment-by-segment image processing. The user observes the image not by way of displays, but rather conventionally by way of optical elements. There is no display of the recorded image in the field glasses. Hence, this binocular system is not the pair of digital field glasses, but rather a pair of conventional analog field glasses, in which a CCD can be inserted merely temporarily in one of the two optical beam paths behind the prism system. While the CCD is inserted into the beam path, this beam path is blocked to the user.
U.S. Pat. No. 7,164,528 B2 proposes to define an image-displaying field on two LCDs in digital field glasses respectively with an objective and a sensor and subsequently to rotate the image on the respective LCDs. Thus, although the user can see a non-reversed and erect, rectangular image in the image-displaying fields within the eyepiece, the image-displaying fields are disadvantageously significantly smaller than the respective LCD, and so a large part of the LCDs remains unused and the LCDs need to be significantly larger than the field which is visible with the respective eyepiece. This can have disadvantageous effects on the costs, the power consumption, the spatial conditions and the configuration of the eyepieces.